Month: April 2019

CPTI Trend with Storm in WFO FWD – 24 April

Posted in Live Blogs on by Michael Bowlan.

Watched the trend in CPTI on the storm in the far southern section of WFO FWD.  This was associated with a cell that straddled the FWD and HGX CWA.  Velocity data showed broad cyclonic rotation that tightened up periodically – including decent GTG.

In terms of CPTI – the probability of the lowest range (80 mph) ranged from 40 to 50% between 2015Z and 2230Z.  As wind speed thresholds increased, the values at 95 and 110mph did not differ much from 80 mph – generally around 40 to 45%.  The highest values of CPTI also remained higher than I might have thought in this case with even the 170mph+ as high as 25%.  This seemed a bit high to me (did not like like an EF4 event) – but maybe statistically this is true???

The merged 0-2km AzShear highlighted this area nicely.  Note, I adjusted the default color table – to cooler colors – e.g. bright white is > 0.015 s-1.  I wouldve loved to view the single radar AzShear product as well!

See AzShear plot at the trends in CPTI below.

GLM Products Identify Hook Echo

Posted in Live Blogs on by Kristin Calhoun.

In our NWS Corpus Christi Warned Storm (ACTUAL NWS CC) The GLM did a fantastic job of identifying the rain wrapped hook echo. I’ve attached visuals and corresponding velocity. Just thought it was pretty neat. The satellite and radar imagery was a little too busy to define it as nicely as the GLM did.

-lakeeffect

ProbSevere Large Areas Impacting Threat Percentages

Posted in Live Blogs, ProbSevere on by Kristin Calhoun.

With this storm going through Milam and Burleson Counties in South Central Texas ProbSevere is saying 90%+ for ProbWind and only like 15% ProbTor. One possible reason for the lower ProbTor may be the large area that ProbSevere is tracking as one storm. Yes, it certainly is one large bowing line segment, but if you look at the AzShear Merged data in the lower right you can see localized maxima in Milam County. While there is not a defined couplet at this point there is some bookend vortex action going on in the area of the AzShear maxima. If the ProbSevere was broken into two different areas would the ProbTor and/or ProbWind be even higher for the Milam County storm due to the locally higher AzShear? I would say probably so! Because ProbSevere is encompassing the entire line segment the values of AzShear going into ProbSevere are probably dampened some from the less active southern part of the storm.

-Alexander T.

HGX Mesoanalysis

Posted in Live Blogs, Mesoscale Discussions on by Michael Bowlan.

Storms are approaching the HGX CWA. GOES-16 imagery shows amply cumulus development across much of the CWA. With temps in the upper 70s and dew points in the upper 60, I expect there to be ample instability in this environment.All Sky LAPS retrievals indicate ML CAPE just shy of 1000 J/kg, but with this environment, I would expect instability to be higher. The modified NUCAPS shows a profile more in line with what I would expect to see. In this profile, the surface dew points were close to what surface obs show, but the surface temp did need to be adjusted up a bit. This sounding, coupled with analyzed deep layer shear, leads me to think severe weather is a possibility in this area.Sandor Clegane

GLM Assist In DSS

Posted in Forecaster Thoughts, Live Blogs, News on by Michael Bowlan.

The below image shows GOES-16 day cloud convection (DCC) beneath GLM Minimum Flash Area (MFA). Point F is a DSS event. DCC shows clouds glaciating a county upstream of our DSS event, with the storm becoming electrified shortly after glaciation per MFA. This prompted a call to the emergency manager providing support for the DSS event letting them know that lightning was imminent.

ENI total lightning also shows lightning (white points), but the point data fails to show the extent of the lightning, which may lead decision makers to think that they have more time to react to the approaching lightning than they actually do.Sandor Clegane

GLM MFA for Storm re-generation

Posted in Forecaster Thoughts, GOESR, Live Blogs on by Kristin Calhoun.

GLM Minimum Flash Area showed some utility in boosting lead time for storm re-generation. The storm in the center of the first image had started to weaken a bit after moving off of the outflow boundary that initiated it.

The storm continues to show no new updraft development in the sat imagery as well as MFA product.

At 20:29 GLM MFA begins to indicate that there may be a new updraft forming as it interacts with a differential heating boundary/outflow from the leading storm.

Over the next 20 minutes the updraft continues to strengthen as the storm becomes more robust. The MFA led the visible satellite depiction of the new updraft by 2-4 min. This could be useful when trying to decide whether to continue warnings or not.

 

 

 

Spike in Merged AzShear Product – Wed Apr 24

Posted in AzShear, HWT on by Michael Bowlan.

Noted a big jump in the merged 0-2km AZshear product – see below.  This caused a corresponding jump in ProbTor.  Also note the “double peak” likely caused by SAILS scans.  This is an a favorable location with > 30kts of 0-3km shear – so mesovortex formation is possible.  Will be interesting to see if anything develops….

 

Waiting on convection – diagnosis and investigation of products

Posted in Forecaster Thoughts, Mesoscale Discussions on by Kristin Calhoun.

Corpus Christi —

In investigating the environment we’ve deemed the convection to be more or less dependent on synoptic forcing via the cold front dropping southeast.

A

In A, plotted is Total Precipitable Water along with SPC Convective Outlook and analyzed fronts. A couple of things can be noted: TPW is very high under the Slight Risk, and it is displayed very nicely with good resolution contained within the gradient. This is a good example without going into too much detail about how our environment is primed for severe weather. However, NUCAPS Gridded Data has not come into our area as of 20z. This makes it hard to test the product and how it captures the boundary layer. 

Now, we wait.

B

As we wait for the cold front to drop SE, our attention is focused on convection happening in NE Mexico (pictured in B). These cells popped up right along the CAPE boundary between values of 300 j/kg to 1500 j/kg.

C

As can be seen in C, the GLM has indicated these storms contain lightning, thus they are intensifying in nature. We will now be monitoring the hail threat.

 

-lakeeffect

All-Sky Gradients & New Storm Development

Posted in Forecaster Thoughts, Mesoscale Discussions on by Kristin Calhoun.

Today was a great example for how the improved resolution from All-Sky LAP allowed us to hone in on exactly where new storm development will occur.  Convection across Mexico developed where the front sagged south along the moisture/CAPE gradient. While in this case the CIRA Merged TPW showed the same gradient, the resolution was still better with All-Sky. Baseline blended TPW as well as satellite derived TPW/CAPE were useless due to either being overly smoothed, or not displaying in cloudy areas. Great diagnostic tool.

— FLGatorDon